Question

define primary key why do we need primary key​

Answer 1

Answer: A primary key is a special relational database table column (or combination of columns) designated to uniquely identify all table records. A primary key's main features are: It must contain a unique value for each row of data. It cannot contain null values.

Explanation: Mark me as brainliest if you mark me as brainliest I will mark u too, follow me and add as friend

Answer 2

Answer:

Abhijit has created three tables and fields are as shown below.  

1. Table 1 - EmpNo, EmpName

2. Table 2- Designation, Department  

3. Table 3- EmpNo, ContactNo

can you tell between which two tables can Abhijit create a relationship

Explanation: